As per ArM5 p180 "Deprivation" - It's a stamina roll with an ease factor that starts at 3, and increases by one for every time period that passes. You will be unlikely to lose more than one fatigue level in the first couple of minutes, as time goes on you're virtually guaranteed to lose a level every 30 seconds.
For concentration - well, it's putting you in danger but not damaging you as quickly as being hit with a weapon, so it's less than 15. Maybe a 12, but a case could be made for 9.